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porky26030
2012-Jan-25, 08:20 AM
Or: Which of These Things is Not Like the Other?

I've recently encountered a fair bit of information regarding Stuff that enters our stellar neighborhood after having formed around other stars, but it's never actually explained how we can tell that matter was formed around a star other than ours, other than being able to say "this particle can only be the byproduct of fusion, and came from thataway, therefore it didn't come from the Sun."

So, my question is this:

Postulate that we have in front of us two icy, rocky asteroid/comet-like objects retrieved from the Oort Cloud that are, for all intents and purposes, identical, but one of them we can definitely say formed in orbit around our very own Sun while the other is a drifter from Alpha Centauri. How do we tell? What techniques do we have to identify what differences between native and newcomer?

Thanks in advance!

chornedsnorkack
2012-Jan-25, 08:31 AM
Main difference is speed.

Jeff Root
2012-Jan-25, 09:14 AM
What the c-horned snorkack means is that we can tell whether
a body has come from inside or outside the Solar System by
the speed it has when we see it flying through Space. So far,
everything we've seen has had a speed too low to say that it
has definitely come from outside the Solar System.

A bit of a letdown, eh?

-- Jeff, in Minneapolis

porky26030
2012-Jan-25, 10:16 PM
Not as much as you'd think, because now I get to imagine a teeny-tiny subatomic particle whipping its near-c way through the galaxy going like this:

http://www.youtube.com/watch?v=hV6PwJ4ZhZg

It's sometimes hard to remember how relative speed can be a small percentage but still a really really big number of miles/kilometres-per-hour.